The present invention relates to the treatment of sludges issuing from a reservoir for purification of waste waters, of the kind comprising a sludge thickener producing an overflowing fluid and a very concentrated sludge which is extracted from the bottom of the thickener.
During this thickening operation, and especially in the case of fermentable organic sludges, the thickeners frequently form the locus of nauseating smell discharges and often have their correct action impeded by fermentation reactions which leads to application of substantial quantities of coagulating and flocculating reactants during the following dehydrating stage. It has already been proposed to provide an oxygenation of the overflowing fluid by dissolution of industrial oxygen which is performed by withdrawing some of the overflowing fluid which is transferred into an industrial oxygenating station and is re-injected into the overflowing fluid. Since it is too primitive, the apparatus proposed is quite inappropriate however to resolve the dual problem of extensive oxygenation of the overflowing fluid which normally requires powerful agitation of the upper portion, that is of the overflowing fluid, keeping the lower portion, meaning the sludges in process of being thickened, in the almost wholly undisturbed condition.